Technical Field
The present invention relates to a field-effect transistor, a display element, an image display, a system, and a composition.
Description of the Related Art
Field effect transistors (FET) control an electric current between a source electrode and a drain electrode according to the principle in which an electric field is applied to a gate electrode to provide a gate against flows of electrons or holes due to an electric field of a channel.
Due to this characteristic, FETs are utilized as switching elements and amplifying elements, etc. Moreover, since FETs have planar configurations and the gate electric current is low, fabrication and integration of FETs are easy in comparison with bipolar transistors. Therefore, FETs are indispensable elements to integrated circuits for use in current electronic devices. FETs are, for example, applied to a display employing active matrix format as thin film transistors (TFTs).
Also, as flat panel displays (FPDs), liquid displays, organic electroluminescence displays, and electronic paper, FETs are put to practical use.
These FPDs are driven by a driving circuit including TFTs using amorphous silicon and polycrystalline silicon, etc. in an active layer. Also, further increase in size, finer resolution, higher image quality, and higher drive response are demanded for FPDs. Accordingly, TFTs are demanded to have an excellent carrier mobility, a high on/off ratio, less temporal change of characteristics, and a small variation between elements.
However, amorphous silicon and polycrystal silicon have both advantages and disadvantages so that it is difficult to satisfy all of the requirements. In attempt to meet the demand, TFTs have been actively developed using an oxide semiconductor in an active layer, which is expected to have mobility better than non-crystal silicon.